Method and apparatus for waste water treatment

ABSTRACT

An apparatus and method for removing contaminants from waste water directs the waste water through a first magnetic field. An ionic polymer is introduced into the waste water after the waste water passes through the first magnetic field, whereby at least some contaminants flocculate. Flocculated contaminants are separated from the waste water so as to form a waste water effluent. An oxidizing agent is introduced into the waste water effluent and the waste water and the oxidizing agent are directed through a second magnetic. The waste water is directed through a weir into a trough open to the atmosphere. Air is injected into the trough so that at least one gas within the waste water combines with the air injected into the waste water. The combined air and gas floats to the surface of the waste water and is expelled into the atmosphere. Foam is removed from the waste water in the trough.

This application is a divisional of, and claims the benefit of,application Ser. No. 08/504,231, filed Jul. 19, 1995 (now U.S. Pat. No.5,783,089), which application is hereby incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to waste water treatment and, inparticular, to removal of solids and dissolved compounds from wastewater.

DESCRIPTION OF THE PRIOR ART

Waste water from poultry processing plants and meat packing plantsgenerally has high concentrations of blood, suspended solids and variousorganic compounds. Suspended solids are often separated from the wastewater, thereby forming a sludge, and the waste water effluent is sent toa water treatment plant for further processing. Because of its highprotein content, the sludge is often sent to a rendering plant forreprocessing as supplements to animal feeds.

Several methods of treating waste water from poultry processing plantsare known in the prior art. These include dissolved air flotation (DAF),which removes suspended solids, oil and grease from waste water by useof dissolved air acting as a buoyant to lift the solids, oil and greaseto the surface of the waste water for removal. Such removal eliminatessome portion of the organic materials in the waste water and thusreduces biochemical oxygen demand (BOD) and chemical oxygen demand(COD). However, DAF has the disadvantage of being ineffective infloating smaller elements of suspended solids and is completelyineffective in removing soluble organic materials.

Induced flocculation, which comprises adding a flocculating agent to thewaste water in the DAF process, causes smaller particles of thesuspended solids to form larger clumps. As a result, the buoyancy of thesolids is enhanced and a greater number of solids are floated to thesurface for removal. The flocculating agents used in the prior artinclude ferric chloride or sulfuric acid added to a polymer. Thecombination of ferric chloride and a polymer is the most widely usedagent. It is marginally effective in reducing biological oxygen demand(BOD) and is almost completely ineffective in reducing the totalKjeldahl nitrogen (TKN) level in the waste water.

Furthermore, ferric chloride tends to cause retention of water in thesludge which requires extensive heating by the rendering plant torecycle the sludge into animal feed supplements. Also, iron tends todegrade the sludge by darkening it and increasing its acidity.

Several biological treatment processes are used to decontaminate wastewater by biologically decomposing organic matter. These types of systemsinclude ammonia nitrogen stripping towers, bio-towers and biologicaltreatment plants. These types of systems have several disadvantages,including: they require substantial capital expenditures, they take uplarge amounts of space, they involve intensive operator monitoring, theyare ineffective where large amounts of oil and grease are present, andthey can be adversely affected by weather conditions.

None of the above methods inexpensively produce high quality sludge andwaste water effluents low in TKN, BOD and COD.

SUMMARY OF THE INVENTION

One aspect of the present invention is an apparatus for removingcontaminants from waste water. It comprises a means for directing thewaste water through a first magnetic field, a means, in fluidcommunication with the directing means, for introducing an ionic polymerinto the waste water after the waste water passes through the firstmagnetic field, whereby at least some contaminants flocculate. A means,downstream of the introducing means, is provided for separatingflocculated contaminants from the waste water so as to form a wastewater effluent.

Another aspect of the present invention is an apparatus for removingcontaminants from waste water that employs a means for adding anoxidizing agent into the waste water. A means, located downstream of theadding means, is provided for directing the waste water and theoxidizing agent through a magnetic field. Also, a means, downstream fromthe directing means, is provided for treating the waste water to causeoffgassing therefrom.

Another aspect of the present invention is a method for removingcontaminants from waste water. The steps followed include: directing thewaste water through a first magnetic field, introducing an ionic polymerinto the waste water that has been directed through the first magneticfield so as to cause at least some of the contaminants to flocculate inthe waste water, and separating the flocculated contaminants from thewaste water after the ionic polymer has been introduced to the wastewater, thereby forming a waste water effluent.

Another aspect of the present invention is a method of removingcontaminants from waste water. The steps followed include adding anoxidizing agent into the waste water, passing the waste water and theoxidizing agent through a magnetic field, and injecting into the wastewater air bubbles that absorb at least one gas from the waste water andthen float to the surface of the waste water and are expelled therefrom.

It is, therefore, an object of the present invention to remove organiccontaminants from waste water.

It is a further object of the present invention to remove dissolvednitrogen from waste water.

It is a further object of the present invention to improve the qualityof effluent sludge from waste water treatment plants.

These and other objects will become apparent from the followingdescription of the preferred embodiment taken in conjunction with thefollowing drawings, although variations and modifications may beeffected without departing from the spirit and scope of the novelconcepts of the disclosure.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS

FIG. 1 is a flow diagram showing the process employed in the presentinvention.

FIG. 2 is a side elevational view of the flocculation unit of thepresent invention.

FIG. 3 is a top plan view of the piping connecting the magnetic waterconditioner to the DAF unit.

FIG. 4 is a top plan view of the off gassing unit of the presentinvention.

FIG. 5 is a side elevational view of the off gassing unit of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the invention is now described in detail.Referring to the drawings, like numbers indicate like parts throughoutthe views.

As used in the description herein and throughout the claims that follow,"a," "an," and "the" includes plural reference unless the contextclearly dictates otherwise. Also as used in the description herein andthroughout the claims that follow, the meaning of "in" includes "in" and"on" unless the context clearly dictates otherwise.

As shown in FIG. 1, the present invention 10 comprises a waste treatmentapparatus for treating the effluent of a producer of waste water. Theapparatus comprises a flocculation unit 20 and an offgassing unit 60.Although the embodiment herein described is directed to treating wastewater from a poultry processing plant, it will be readily understoodthat any producer of organic-rich waste water (including sewage plants,paper mills and the like) will benefit from the present invention 10.

Initially, in the flocculating unit 20, an oxidizing agent 22, such ascalcium hypochlorite, sodium hypochlorite or hydrogen peroxide ispreferably injected into the waste water stream near the influent 12 ofthe flocculating unit 20. This oxidizing agent 22 is preferred when theprocessing plant is marinating poultry with liquids rich in sodiumchloride or soluble BOD. It is believed that the oxidizing agent helpsto remove the dissolved salts. The waste water is directed into a firstmagnetic water conditioner 24 where it passes through a first magneticfield. The magnetic water conditioner 24 employed in the presentinvention may be of the type disclosed in, for example, U.S. Pat. Nos.3,951,807, 4,153,559, 4,299,559, and 4,357,237, all issued to Sandersonand incorporated herein by reference. Such magnetic water conditionersare available from Superior Water Conditioners of Fort Wayne, Ind.Furthermore, other methods of generating magnetic fields, such aselectromagnets, will work with the present invention. Furthermore, theuse of an electric field may accomplish the same result as a magneticfield. After exiting the magnetic water conditioner 24, an ionic polymer26 is injected into the waste water stream. Depending on thecontaminants being removed, the ionic polymer may be either cationic oranionic of any of the types well known in the art. One preferredcationic polymer is RS1285 available from R-Square of Gainesville, Ga.The waste water is then directed into a conventional DAF 28 where someof the organic compounds and solids flocculate and eventually arecarried off as sludge 30.

The waste water from the flocculating unit 20 is then passed into theoffgassing unit 60. Initially, an oxidizing agent 62 such as calciumhypochlorite is injected into the waste water stream. The combination ofthe waste water and the oxidizing agent 62 is passed through a secondmagnetic water conditioner 64, of the type described above. From thesecond magnetic water conditioner 64, the waste water is passed into anoff-gassing trough 66 where it gives off gasses 68 and discharges sludge70. The waste water is then passed into a final clarifier 80 where moresludge 70 is removed and the waste water exits the system as an effluent90. The waste water is then either recycled or discarded.

As shown in FIG. 2, the flocculating unit 20 comprises a conventionalDAF 28 connected to a magnetic water conditioner 24. The influent 12from the processing plant is received by the DAF 28 and directed throughthe magnetic water conditioner 24. FIG. 3 is a top plan view of thepiping connecting the DAF 28 to the magnetic water conditioner 24. Anoxidizing agent 22 is preferably injected into the waste water prior toentering the magnetic water conditioner 24 and an ionic polymer 26 isadded to the waste water after it exits the magnetic water conditioner22. The addition of the oxidizing agent 22 is preferable if theprocessing plant is performing a marinating process using sodiumchloride, or other similar salts, as the purpose of the oxidizing agent22 in the flocculating unit 20 is to remove salt that would otherwisecause a breakdown of the ionic polymer 26.

Returning to FIG. 2, waste water that has exited the magnetic waterconditioner 24 and that has had the ionic polymer 26 injected isdirected into a mixing chamber 32 in which contaminants in the wastewater will tend to flocculate. The waste water is then directed to afloat removal system 30 where the flocculated contaminants are separatedfrom the waste water and removed as sludge, with the remaining wastewater forming an effluent.

As shown in FIGS. 4 and 5, effluent 36 from the flocculating unit 20 isdirected into the offgassing unit 66. A second oxidizing agent 62, suchas calcium hypochlorite, sodium hypochlorate or hydrogen peroxide isinjected into the waste water stream with a metering pump 63. The wastewater is directed through a second magnetic field in a second magneticwater conditioner 64. The waste water then flows through a plurality ofweirs 100 into a trough 110 that is exposed to the atmosphere. An airinjection system 160 then injects air bubbles into the waste water inthe trough 110 to aid in removing gasses exiting the waste water in thetrough 110. It is believed that the gasses removed comprise nitrogengasses.

The trough 110 comprises a frame 112 having a bottom 114 with twoparallel vertical opposed side walls 116 extending upwardly therefrom.The sidewalls 116 have a first side edge 120 and an opposite second sideedge 120 and define a cavity 118 therebetween.

The air injection system 160 injects air into the waste water in thetrough 110. The air injection system 160 comprises a plurality ofblowers 166 that pump air into a header 162, which delivers air to aplurality of air manifolds 164 disposed near the bottom of the trough110. Air exiting the manifolds 164 forms bubbles in the waste water soat least one gas within the waste water combines with the air injectedinto the waste water, floats to the surface of the waste water with theinjected air and is expelled into the atmosphere.

Typically, the air bubbles injected into the waste water will form afoam at the surface of the waste water that interferes with offgassing.Therefore, a foam removal system 140 is disposed within the trough 110.The foam removal system 140 comprises a plurality of upright, opposedmembers 144 in the trough, each member 144 being in opposed relationshipto another member 144 and comprising a pair of spaced-apart element s142 upwardly extending from the bottom 114 of the trough 110 and forminga channel 146 therebetween. Each element 142 terminates in a top end 148which is above the surface of the waste water in the trough so that asfoam builds up on the surface of the waste water above the top ends 148,the foam will fall into the channel 146. The elements 142 are laterallydisposed within the trough 110 such that the first ends 150 of a firstamount of the elements 142 abut the inside surface of one of the sidewalls 116. The respective second ends 152 of the elements 142 areadjacent to the opposite other sidewall 116 in alternate relationship tothe remaining elements 142 that have their second ends 152 abut theinside surface of the opposite side wall 116. Thus, the elements 142form a circuitous path thereamong for the waste water to flow. Also, asluice gate 170 is provided to raise the level of the waste water to alevel adjacent the top ends 148 of each element 142, thereby increasingthe amount of foam that will fall into the channel 146. In alternativeembodiments, foam may be removed from the surface of the waste watereither by scraping or vacuuming therefrom.

To enhance offgassing, a recirculation line 182 and a recirculating pump180 may be added to recirculate waste water, rich in dissolved air, fromthe trough 110 back into the effluent 36 from the flocculating unit 20.The waste water recirculated from the recirculating pump 180 may also bedirected through a third magnetic field in a third magnetic waterconditioner 184 to further enhance offgassing.

Waste water exiting the trough 110 is then passed into a final clarifier190, which comprises a conventional drag conveyor 194. The finalclarifier 190 removes remaining solids or foam in the waste water anddeposits them in a scum pit 192 that allows the solids and foam tosettle, discharging them to a sludge discharge 70. The waste water isthen directed to a discharge 196 where it is recycled by the processingplant or otherwise discarded.

It is to be understood by those skilled in the art that, depending uponthe application, either of the flocculating unit 22 or the offgassingunit 60 could be used by itself or that the order of their employmentcould be reversed from that described above without departing from thescope of the invention.

EXAMPLE

The following is a comparison of a composite sampling result taken overa 24-hour period from the same waste stream. This sample was treated bya producer of waste water by the old method (a physical/chemical unitusing ferric chloride and a treatment polymer) and by the methodemployed in the present invention. The surcharge limit for a parameteris the contaminant level above which local waste treatment facilitiescharge an additional fee for receiving waste water. The violation limitis the level above which local waste water treatment facilities mayrefuse to accept waste water.

    __________________________________________________________________________                         Sampling Result                                                                       Sampling Result                                     Surcharge Violation Employing the Employing the                              Parameter Limit Limit Old Method Present Invention                          __________________________________________________________________________    B.O.D. 5                                                                             250 mg/l                                                                             501 mg/l                                                                             240 mg/l                                                                              150 mg/l                                           T.S. Solids 250 mg/l 501 mg/l 35 mg/l 27 mg/l                                 Oil and Grease 100 mg/l 126 mg/l 5 mg/l BDL                                   Phosphorus 10 mg/l 16 mg./ 6.7 mg/l 7.6 mg/l                                  TKN 40 mg/l 76 mg/l 65.4 mg/l 16 mg/l                                         pH 6.09-9.5 units 6.09-9.5 units 6.2 units 7.0 units                        __________________________________________________________________________     BDL = Below detection limit                                              

BOD5 is a measure of the biological oxygen demand and T.S.Solids is ameasure of the total suspended solids.

The net cost of treating waste water with the present invention is lessthan the net cost of older methods of treatment. The concept of net costincludes a reduced treatment costs and higher selling prices for thesludge by-product created with this method of waste water treatment. Ahigher selling price for sludge generated by this method of treatment isattributable to: 1.) a better quality sludge due to the absence of ironor acids; and 2.) a dryer sludge attributable to the absence of thewater retaining characteristics of iron. A dryer sludge is more valuableas a raw material or supplement for animal foods because of the lowerenergy cost required to cook the product. Added advantages of thepresent invention include: 1.) due to better effluent quality, the wastestream may be recycled or reused; 2.) it results in lowered or avoidedsurcharges from regulatory agencies for lack of compliance withconventional pollutant standards; and 3.) users may realize cost savingson oxidizing agents used as an alternative to the ferric chlorideemployed in the prior art.

The above described embodiments are given as illustrative examples only.It will be readily appreciated that many deviations may be made from thespecific embodiments disclosed in this specification without departingfrom the invention. Accordingly, the scope of the invention is to bedetermined by the claims below rather than being limited to thespecifically described embodiments above.

What is claimed is:
 1. An apparatus for removing contaminants from wastewater, comprising:a. means for directing the waste water through a firstmagnetic field; b. means, in fluid communication with the directingmeans, for introducing an ionic polymer into the waste water after thewaste water passes through the first magnetic field, whereby at leastsome contaminants flocculate; and c. a dissolved air flotation unit,downstream of the introducing means, that injects air into the wastewater so that the air acts as a buoyant to lift flocculated contaminantsto the waste water surface, and that removes the flocculatedcontaminants from the surface of the waste water.
 2. The apparatus ofclaim 1 further comprising means for adding an oxidizing agent to thewaste water prior to the waste water being directed through the firstmagnetic field.
 3. The apparatus of claim 1 wherein the directing meanscomprises a magnetic water conditioner.
 4. The apparatus of claim 1wherein the ionic polymer is a cationic polymer.
 5. The apparatus ofclaim 1 wherein the ionic polymer is an anionic polymer.
 6. An apparatusfor removing contaminants from waste water, comprising:a. a magneticwater conditioner that directs the waste water through a first magneticfield; b. a device, in fluid communication with the magnetic waterconditioner, for introducing an ionic polymer into the waste water afterthe waste water passes through the first magnetic field, whereby atleast some contaminants flocculate; and c. a dissolved air flotationunit, downstream of the introducing means, that injects air into thewaste water so that the air acts as a buoyant to lift flocculatedcontaminants to the waste water surface, and that removes theflocculated contaminants from the surface of the waste water.
 7. Amethod for removing contaminants from waste water, comprising:a.directing the waste water through a first magnetic field; b. introducingan ionic polymer into the waste water after the waste water passesthrough the first magnetic field, thereby causing at least somecontaminants flocculate; and c. injecting air into the waste water sothat the air acts as a buoyant to lift flocculated contaminants to thewaste water surface; and d. removing the flocculated contaminants fromthe surface of the waste water.